Inkjet printing mechanisms use cartridges, often called “pens,” which eject drops of liquid colorant, referred to generally herein as “ink,” onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. Although not completely, strictly accurate, practitioners often refer to the whole printhead assembly as “silicon”. The terminology “separate ink and silicon” refers to a system where the primary ink reservoir is not a permanent part of the printhead assembly. To print an image, the printhead is propelled back and forth across the page, selectively ejecting drops of ink in a desired pattern. The ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezo-electric or thermal printhead technology.
Early inkjet printers used a single monochromatic pen, typically carrying black ink. Later generations of inkjet printing mechanisms used a black pen which was interchangeable with a tri-color pen, typically one carrying the colors of cyan, magenta, and yellow within a single cartridge. The tri-color pen printed a “process” or “composite” black image, by depositing drops of cyan, magenta, and yellow inks all at the same location. The next generation of printers further enhanced the images produced by using either a dual pen system or a quad pen system. The dual pen printers had a black pen and a tri-color pen mounted in a single carriage to print crisp, clear black text while providing full color images.
The quad pen printing mechanisms had four separate pens that carried black ink, cyan ink, magenta ink, and yellow ink. Quad pen plotters typically carried four pens in four separate carriages. Similarly, quad pen desktop printers were designed to carry four cartridges in a single carriage, each cartridge and pen adding to the weight of the inkjet printing mechanisms.
As the number of pens incorporated by inkjet printing mechanisms increased, the cost and size of the inkjet printing mechanisms also increased due to the increased quantity of ink contained by the cartridges. In order to carry enough ink for high ink use applications, the carriage must be large enough to carry large (10 or more cc's) ink supply cartridges of all colors. This requires significant power to move the carriage and large printer size to accommodate the volume of the carriage; each of these factors increasing the cost of the printer. Recently, efforts have been made to reduce the cost and size of ink-jet printers.
However, reducing the cost and size of inkjet printers by reducing the volume of ink supplied to each pen limits the inkjet printers to small print jobs and increases the frequency of ink replacement. Furthermore, whenever an ink supply cartridge on a low volume inkjet printer is emptied, direct operator intervention is required before printing can resume.
Consequently, different carriage designs have been implemented to optimally address high and low ink use applications. When incorporating expensive large printers, valuable space on a user's desktop is consumed. However, when incorporating smaller printers, ink replacement is frequently needed demanding direct intervention by a user. Moreover, addressing various ink usage rates with multiple ink supply cartridge sizes is costly since production lines must be designed to accommodate multiple cartridge sizes, inventories of raw materials and production plans must be managed, and the distribution system must manage multiple stock keeping units (SKU's).